1. Field of the Invention
The present invention relates to an organic material applying apparatus for applying an organic material onto an upper surface of a semiconductor wafer in a manufacturing process of a semiconductor device, and more particularly to an organic material applying apparatus for applying an organic material onto a semiconductor wafer wherein the amount of that portion of the organic material, which is not retained on the surface of the wafer and wasted, is reduced and thereby the organic material is used efficiently.
2. Description of the Related Art
The performance and integration density of state-of-the-art semiconductor devices are enhanced, and very precise alignment, as well as miniaturization and uniformity, is required for lithographic technology used in the manufacturing process of the semiconductor devices. A spin-coating method has conventionally been adopted in an organic material applying apparatus for applying an organic material such as photoresist material, which is essential to lithographic technology, to the upper surface of a semiconductor wafer.
FIG. 1 is a view for generally illustrating a conventional resist applying method according to spin-coating.
Specifically, a drop of photoresist material 73 is fallen from a nozzle 72 onto a semiconductor wafer 71 and then the wafer 71 is rotated. Thereby, the photoresist material 73 is spread over the semiconductor wafer 71, and it is coated on the wafer 71.
However, according to the spin-coating resist applying method, the ratio of the resist material remaining on the wafer to the entire resist material discharged from the nozzle is several %, and more than 90% of the discharged material is wasted during spreading and coating. Thus, the photoresist material is considerably wasted.
On the other hand, in order to efficiently use the resist material, a blade dispense nozzle method has been proposed. According to this method, the wafer need not be rotated, and more than 90% of the entire resist material discharged from the nozzle can be left on the wafer, while the resist material wasted is reduced to 10% or less.
FIG. 2 is a plan view showing schematically the structure of an important portion of a photoresist applying apparatus according to a conventional blade dispense method.
Specifically, while a dispense nozzle 2 is moved in the direction of arrow A over the upper surface of a stationary semiconductor wafer 1, a photoresist material is jetted from a distal end portion of the nozzle 2 and coated on the surface of the wafer 1. In this case, the velocity of movement of the wafer 1 and the rate of discharge of the photoresist material are controlled, thereby controlling the thickness of a photoresist film formed on the semiconductor wafer 1.
However, in the actual wafer processing, the rate of discharge of photoresist material is constant, although the width of the portion of the wafer, which the dispense nozzle 2 faces successively, varies while the photoresist film is coated on the semiconductor wafer 1 by the photoresist applying apparatus shown in FIG. 2. Thus, when the dispense nozzle 2 faces a narrow portion of the wafer 1, the resist material, the amount of which is greater than necessary, is discharged on the wafer 1 and a considerable amount of resist material is lost.
In addition, when a photoresist film is coated on the semiconductor wafer 1 by the photoresist applying apparatus shown in FIG. 2, the photoresist film adheres to the peripheral portion of the wafer 1, too. Consequently, it is necessary to provide a step for removing the unnecessary photoresist film on the peripheral portion of the wafer after the coating of the photoresist. Dust occurring in this step may result in occurrence of particles while the wafer is moved in subsequent steps (e.g. pattern etching).